Red Bull's Sebastian Vettel may have topped Friday practice ahead of the European Grand Prix, but the double world champion is taking nothing for granted ahead of Sunday's race.

The German's lap of one minute 39.334 seconds around the Valencia street circuit eclipsed the effort of Force India's Niko Hulkenberg by 0.1 secs, but Vettel expects it to have little bearing on the season's eighth grand prix of the year.

"We have tried some new parts on the car today, but the lap times have not really allowed us to have a fair conclusion of them yet," the 24-year-old told Formula One's official website.

"It was important to have a clean practice today and I'm happy with what we did. The conditions will change again for Sunday I think; it was a bit cooler today, which will make a difference.

"It's close between the teams and it's not yet clear what the right strategy is for Sunday, hopefully we can make a step forward tomorrow."

"Overall, it's been a positive day, during which we tried various updates on the car," said the 30-year-old.

"Some worked well, others need some modifying and then they might be used at Silverstone (on July 8 for the British GP.)

"Hamilton is ahead of me, so the objective is to leave Valencia ahead of him and then, maybe in Silverstone, Vettel will be first, so he will be the target."

Mercedes' Michael Schumacher was fourth on the time sheets, continuing the speed he displayed over the street circuit of Monte Carlo last month.

"Our work today was reasonably good, with obviously a lot of data to be confirmed now in our technical briefings before qualifying. The second session initially started with an issue with the clutch but it turned out very ok." said the seven-time champion.

"Of course we are aware that it will be a challenge for everybody, especially to keep the rear tires alive but this is as expected. Let's see what we can do tomorrow."